Captain was a rank in the Imperial Army, the Grand Army of the Republic (GAR), and many others. In most naval forces, such as the Republic Navy and the Marine Corps, it was held by warship commanders and senior field officers, though the title was also used to refer to officers appointed to command smaller vessels despite holding a lesser rank.

Within ground-based martial services such as the Republic Army, captains typically led company-sized formations, or else served as outpost commanders. Among Mandalorians and other mercenaries, the honorific of captain usually denoted the head of a particular mercenary band.